<template>
  <table
    cellspacing="0"
    cellpadding="0"
    class="el-date-table herin-el-date-table"
    :class="{ 'is-week-mode': selectionMode === 'week' }"
    @click="handleClick"
    @mousemove="handleMouseMove"
  >
    <tbody>
      <tr>
        <th v-if="showWeekNumber">{{ t('el.datepicker.week') }}</th>
        <th v-for="(week, key) in WEEKS" :key="key">{{ t('el.datepicker.weeks.' + week) }}</th>
      </tr>
      <tr
        v-for="(row, key) in rows"
        :key="key"
        class="el-date-table__row"
        :class="{ current: isWeekActive(row[1]) }"
      >
        <td
          v-for="(cell, index) in row"
          :key="index"
          :class="getCellClasses(cell)"
        >
          <div class="el-date-table__row_item_div">
            <span>
              {{ cell.text }}
            </span>
          </div>
        </td>
      </tr>
    </tbody>
  </table>
</template>

<script>
import { getFirstDayOfMonth, getDayCountOfMonth, getWeekNumber, getStartDateOfMonth, prevDate, nextDate, isDate, clearTime as _clearTime } from 'element-ui/src/utils/date-util';
import Locale from 'element-ui/src/mixins/locale';
import { arrayFindIndex, arrayFind, coerceTruthyValueToArray } from 'element-ui/src/utils/util';

const WEEKS = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'];
const getDateTimestamp = function(time) {
  if (typeof time === 'number' || typeof time === 'string') {
    return _clearTime(new Date(time)).getTime();
  } else if (time instanceof Date) {
    return _clearTime(time).getTime();
  } else {
    return NaN;
  }
};

// remove the first element that satisfies `pred` from arr
// return a new array if modification occurs
// return the original array otherwise
const removeFromArray = function(arr, pred) {
  const idx = typeof pred === 'function' ? arrayFindIndex(arr, pred) : arr.indexOf(pred);
  return idx >= 0 ? [...arr.slice(0, idx), ...arr.slice(idx + 1)] : arr;
};

export default {
  mixins: [Locale],

  props: {
    firstDayOfWeek: {
      default: 7,
      type: Number,
      validator: val => val >= 1 && val <= 7
    },

    // value: {
    //   type: Object,
    //   default: () => {}
    // },
    value: [Object, String, Date],

    defaultValue: {
      type: Object,
      default: () => null,
      validator(val) {
        // either: null, valid Date object, Array of valid Date objects
        return val === null || isDate(val) || (Array.isArray(val) && val.every(isDate));
      }
    },

    // date: {
    //   type: Object,
    //   default: () => {}
    // },
    date: [Object, String, Date],

    selectionMode: {
      type: String,
      default: 'day'
    },

    showWeekNumber: {
      type: Boolean,
      default: false
    },

    disabledDate: [Object, String, Function],
    // disabledDate: {
    //   type: Object,
    //   default: () => {}
    // },

    cellClassName: [Object, String],
    // cellClassName: {
    //   type: Object,
    //   default: () => {}
    // },

    minDate: {
      type: Object,
      default: () => {}
    },

    maxDate: {
      type: Object,
      default: () => {}
    },

    rangeState: {
      type: Object,
      default: () => {
        return {
          endDate: null,
          selecting: false
        };
      }
    }
  },

  data() {
    return {
      tableRows: [[], [], [], [], [], []],
      lastRow: null,
      lastColumn: null
    };
  },

  computed: {
    offsetDay() {
      const week = this.firstDayOfWeek;
      // 周日为界限，左右偏移的天数，3217654 例如周一就是 -1，目的是调整前两行日期的位置
      return week > 3 ? 7 - week : -week;
    },

    WEEKS() {
      const week = this.firstDayOfWeek;
      return WEEKS.concat(WEEKS).slice(week, week + 7);
    },

    year() {
      return this.date.getFullYear();
    },

    month() {
      return this.date.getMonth();
    },

    startDate() {
      return getStartDateOfMonth(this.year, this.month);
    },

    rows() {
      // TODO: refactory rows / getCellClasses
      const date = new Date(this.year, this.month, 1);
      let day = getFirstDayOfMonth(date); // day of first day
      const dateCountOfMonth = getDayCountOfMonth(date.getFullYear(), date.getMonth());
      const dateCountOfLastMonth = getDayCountOfMonth(date.getFullYear(), (date.getMonth() === 0 ? 11 : date.getMonth() - 1));

      day = (day === 0 ? 7 : day);

      const offset = this.offsetDay;
      const rows = this.tableRows;
      let count = 1;

      const startDate = this.startDate;
      const disabledDate = this.disabledDate;
      const cellClassName = this.cellClassName;
      const selectedDate = this.selectionMode === 'dates' ? coerceTruthyValueToArray(this.value) : [];
      const now = getDateTimestamp(new Date());

      for (let i = 0; i < 6; i++) {
        const row = rows[i];

        if (this.showWeekNumber) {
          if (!row[0]) {
            row[0] = { type: 'week', text: getWeekNumber(nextDate(startDate, i * 7 + 1)) };
          }
        }

        for (let j = 0; j < 7; j++) {
          let cell = row[this.showWeekNumber ? j + 1 : j];
          if (!cell) {
            cell = { row: i, column: j, type: 'normal', inRange: false, start: false, end: false };
          }

          cell.type = 'normal';

          const index = i * 7 + j;
          const time = nextDate(startDate, index - offset).getTime();
          cell.inRange = time >= getDateTimestamp(this.minDate) && time <= getDateTimestamp(this.maxDate);
          cell.start = this.minDate && time === getDateTimestamp(this.minDate);
          cell.end = this.maxDate && time === getDateTimestamp(this.maxDate);
          const isToday = time === now;

          if (isToday) {
            cell.type = 'today';
          }

          if (i >= 0 && i <= 1) {
            const numberOfDaysFromPreviousMonth = day + offset < 0 ? 7 + day + offset : day + offset;

            if (j + i * 7 >= numberOfDaysFromPreviousMonth) {
              cell.text = count++;
            } else {
              cell.text = dateCountOfLastMonth - (numberOfDaysFromPreviousMonth - j % 7) + 1 + i * 7;
              cell.type = 'prev-month';
            }
          } else {
            if (count <= dateCountOfMonth) {
              cell.text = count++;
            } else {
              cell.text = count++ - dateCountOfMonth;
              cell.type = 'next-month';
            }
          }

          const cellDate = new Date(time);
          cell.disabled = typeof disabledDate === 'function' && disabledDate(cellDate);
          cell.selected = arrayFind(selectedDate, date => date.getTime() === cellDate.getTime());
          cell.customClass = typeof cellClassName === 'function' && cellClassName(cellDate);
          // eslint-disable-next-line vue/no-side-effects-in-computed-properties
          this.$set(row, this.showWeekNumber ? j + 1 : j, cell);
        }

        if (this.selectionMode === 'week') {
          const start = this.showWeekNumber ? 1 : 0;
          const end = this.showWeekNumber ? 7 : 6;
          const isWeekActive = this.isWeekActive(row[start + 1]);

          row[start].inRange = isWeekActive;
          row[start].start = isWeekActive;
          row[end].inRange = isWeekActive;
          row[end].end = isWeekActive;
        }
      }

      return rows;
    }
  },

  watch: {
    'rangeState.endDate'(newVal) {
      this.markRange(this.minDate, newVal);
    },

    minDate(newVal, oldVal) {
      if (getDateTimestamp(newVal) !== getDateTimestamp(oldVal)) {
        this.markRange(this.minDate, this.maxDate);
      }
    },

    maxDate(newVal, oldVal) {
      if (getDateTimestamp(newVal) !== getDateTimestamp(oldVal)) {
        this.markRange(this.minDate, this.maxDate);
      }
    }
  },

  methods: {
    cellMatchesDate(cell, date) {
      const value = new Date(date);
      return this.year === value.getFullYear() &&
          this.month === value.getMonth() &&
          Number(cell.text) === value.getDate();
    },

    getCellClasses(cell) {
      const selectionMode = this.selectionMode;
      const defaultValue = this.defaultValue ? Array.isArray(this.defaultValue) ? this.defaultValue : [this.defaultValue] : [];

      const classes = [];
      if ((cell.type === 'normal' || cell.type === 'today') && !cell.disabled) {
        classes.push('available');
        if (cell.type === 'today') {
          classes.push('today');
        }
      } else {
        classes.push(cell.type);
      }

      if (cell.type === 'normal' && defaultValue.some(date => this.cellMatchesDate(cell, date))) {
        classes.push('default');
      }

      if (selectionMode === 'day' && (cell.type === 'normal' || cell.type === 'today') && this.cellMatchesDate(cell, this.value)) {
        classes.push('current');
      }

      if (cell.inRange && ((cell.type === 'normal' || cell.type === 'today') || this.selectionMode === 'week')) {
        classes.push('in-range');

        if (cell.start) {
          classes.push('start-date');
        }

        if (cell.end) {
          classes.push('end-date');
        }
      }

      if (cell.disabled) {
        classes.push('disabled');
      }

      if (cell.selected) {
        classes.push('selected');
      }

      if (cell.customClass) {
        classes.push(cell.customClass);
      }

      return classes.join(' ');
    },

    getDateOfCell(row, column) {
      const offsetFromStart = row * 7 + (column - (this.showWeekNumber ? 1 : 0)) - this.offsetDay;
      return nextDate(this.startDate, offsetFromStart);
    },

    isWeekActive(cell) {
      if (this.selectionMode !== 'week') return false;
      const newDate = new Date(this.year, this.month, 1);
      const year = newDate.getFullYear();
      const month = newDate.getMonth();

      if (cell.type === 'prev-month') {
        newDate.setMonth(month === 0 ? 11 : month - 1);
        newDate.setFullYear(month === 0 ? year - 1 : year);
      }

      if (cell.type === 'next-month') {
        newDate.setMonth(month === 11 ? 0 : month + 1);
        newDate.setFullYear(month === 11 ? year + 1 : year);
      }

      newDate.setDate(parseInt(cell.text, 10));

      if (isDate(this.value)) {
        const dayOffset = (this.value.getDay() - this.firstDayOfWeek + 7) % 7 - 1;
        const weekDate = prevDate(this.value, dayOffset);
        return weekDate.getTime() === newDate.getTime();
      }
      return false;
    },

    markRange(minDate, maxDate) {
      minDate = getDateTimestamp(minDate);
      maxDate = getDateTimestamp(maxDate) || minDate;
      [minDate, maxDate] = [Math.min(minDate, maxDate), Math.max(minDate, maxDate)];

      const startDate = this.startDate;
      const rows = this.rows;
      for (let i = 0, k = rows.length; i < k; i++) {
        const row = rows[i];
        for (let j = 0, l = row.length; j < l; j++) {
          if (this.showWeekNumber && j === 0) continue;

          const cell = row[j];
          const index = i * 7 + j + (this.showWeekNumber ? -1 : 0);
          const time = nextDate(startDate, index - this.offsetDay).getTime();

          cell.inRange = minDate && time >= minDate && time <= maxDate;
          cell.start = minDate && time === minDate;
          cell.end = maxDate && time === maxDate;
        }
      }
    },

    handleMouseMove(event) {
      if (!this.rangeState.selecting) return;

      let target = event.target;
      if (target.tagName === 'SPAN') {
        target = target.parentNode.parentNode;
      }
      if (target.tagName === 'DIV') {
        target = target.parentNode;
      }
      if (target.tagName !== 'TD') return;

      const row = target.parentNode.rowIndex - 1;
      const column = target.cellIndex;

      // can not select disabled date
      if (this.rows[row][column].disabled) return;

      // only update rangeState when mouse moves to a new cell
      // this avoids frequent Date object creation and improves performance
      if (row !== this.lastRow || column !== this.lastColumn) {
        this.lastRow = row;
        this.lastColumn = column;
        this.$emit('changerange', {
          minDate: this.minDate,
          maxDate: this.maxDate,
          rangeState: {
            selecting: true,
            endDate: this.getDateOfCell(row, column)
          }
        });
      }
    },

    handleClick(event) {
      let target = event.target;
      if (target.tagName === 'SPAN') {
        target = target.parentNode.parentNode;
      }
      if (target.tagName === 'DIV') {
        target = target.parentNode;
      }

      if (target.tagName !== 'TD') return;

      const row = target.parentNode.rowIndex - 1;
      const column = this.selectionMode === 'week' ? 1 : target.cellIndex;
      const cell = this.rows[row][column];

      // console.log(cell);
      if (cell.disabled || cell.type === 'week' || cell.type === 'next-month' || cell.type === 'prev-month') return;

      const newDate = this.getDateOfCell(row, column);

      if (this.selectionMode === 'range') {
        if (!this.rangeState.selecting) {
          this.$emit('pick', { minDate: newDate, maxDate: null });
          // eslint-disable-next-line vue/no-mutating-props
          this.rangeState.selecting = true;
        } else {
          if (newDate >= this.minDate) {
            this.$emit('pick', { minDate: this.minDate, maxDate: newDate });
          } else {
            this.$emit('pick', { minDate: newDate, maxDate: this.minDate });
          }
          // eslint-disable-next-line vue/no-mutating-props
          this.rangeState.selecting = false;
        }
      } else if (this.selectionMode === 'day') {
        this.$emit('pick', newDate);
      } else if (this.selectionMode === 'week') {
        const weekNumber = getWeekNumber(newDate);
        const value = newDate.getFullYear() + 'w' + weekNumber;
        this.$emit('pick', {
          year: newDate.getFullYear(),
          week: weekNumber,
          value: value,
          date: newDate
        });
      } else if (this.selectionMode === 'dates') {
        const value = this.value || [];
        const newValue = cell.selected
          ? removeFromArray(value, date => date.getTime() === newDate.getTime())
          : [...value, newDate];
        this.$emit('pick', newValue);
      }
    }
  }
};
</script>

<style lang="scss">
.herin-el-date-table{
  .in-range{
    .el-date-table__row_item_div{
      background-color: rgba($color: #fff, $alpha: 0.3);
    }
  }
  .el-date-table__row td.disabled div{
    background-color: rgba($color: #fff, $alpha: 0.2);
  }
  th{
    font-size: 0.75rem;
  }
  .el-date-table__row{
    td{
      padding: .25rem 0;
      width: 2rem;
      height: 1.875rem;
      font-size: 0.75rem;
      &.start-date div {
        margin-left: .3125rem;
        border-top-left-radius: .9375rem;
        border-bottom-left-radius: .9375rem;
      }
      div{
        height: 1.875rem;
        padding: .1875rem 0;
      }
      span{
        width: 1.5rem;
        height: 1.5rem;
        line-height: 1.5rem;
      }
    }
    .prev-month{
      cursor: not-allowed;
    }
    .next-month{
      cursor: not-allowed;
    }
  }
}
</style>
